Method of preventing adherence of a second coating to a fastener portion

ABSTRACT

Accordingly, this invention provides a fastener system which is weldable to a substructure that overcomes the problems and disadvantages of the fasteners of the prior art. Generally, a weldable fastener is disclosed that has a coating applied to at least one surface of the fastener. The coating functions to prevent the deposit of a further coating, particularly an electrodeposition coating, upon further processing.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional application of U.S. patent applicationSer. No. 10/441,843, filed on May 20, 2003 (now U.S. Pat. No. 7,021,875issued on Apr. 4, 2006), which claims the benefit of U.S. ProvisionalApplication No. 60/458,865, filed on Mar. 28, 2003. U.S. patentapplication Ser. No. 10/441,843 is a continuation-in-part application ofPCT International Application PCT/US02/34608, which was filed in theU.S. Receiving Office on Oct. 30, 2002. PCT International ApplicationNo. PCT/US02/34608 claims the benefit of U.S. Provisional ApplicationNo. 60/340,905, filed on Oct. 30, 2001; U.S. Provisional Application No.60/391,809, filed on Jun. 25, 2002; and U.S. Provisional Application No.60/398,258, filed on Jul. 24, 2002. The disclosures of the aboveapplications are incorporated herein by reference.

FIELD OF THE INVENTION

The present invention relates to a coated fastener and particularly to awelded coated fastener having a coating that resists the adherence of anelectrodeposited coating. The present invention further relates tovehicle assembly methods and other assembly methods in which fastenersare attached and coupled together.

BACKGROUND OF THE INVENTION

With ever increasing design demands, flexibility and adaptivity ofunibody construction is increasingly required in order to providevehicles that meet broader customer needs. Increases in the number ofcomponents and structures that are coupled to the unibody constructionhave led designers to consistently add threaded fasteners to the unibodyframe. Variation in manufacturing tolerances require that the fastenercouple to the unibody frame in a way that allows a degree of positionaladjustment during final assembly. This positional adjustment is providedby using a female fastener that is an encaged fastener. Typically, thistakes the form of a nut or fastener encaged in a structure that isattached to the inner body frame. The cage is configured to provide thenut with a range of movement so that when a component is coupled to theframe, the alignment of the component and frame can be adjusted untilthey meet manufacturing standards.

Prior to coupling of the components to the frame, however, the framestypically are painted or coated using electrocoat e-coat orelectrodeposition coating processes. To date, the step of electrocoatingthe frame often results in the electrocoat paint adhering to thefastener or, with a caged fastener, causes the fastener to adhere to thecage. This prevents the fastener from being adjustable within the cageand, therefore, causes tolerance problems in the final assembly of theproduct. In the case of threaded fasteners, the application of theelectrocoat paint to the fastener's threads increases problems in thecoupling of a mating fastener. To prevent the tolerance problems,post-process inspection after painting is required to ensure that thefasteners are not adhered to the cage or fastener thread. Should postpainting of the threads occur or the fastener become adhered to the cageby the electrocoat coating, post-process rework must be conducted toclean the fastener.

SUMMARY OF THE INVENTION

Accordingly, this invention provides a fastener system that is weldableto a substructure that overcomes the problems and disadvantages of thefasteners of the prior art. Generally, a weldable fastener is disclosedthat has a coating applied to at least one surface of the fastener. Inone embodiment, the invention includes a threaded fastener in a fastenercage capable of fastening the fastener to a substructure, the cagehaving a coating which inhibits additional coatings, particularly anelectrodeposition coating, from sticking to the cage.

In accordance with the teachings of another embodiment of the presentinvention, there is provided a weld stud assembly for use with a drawnarc welding system that overcomes the deficiencies of the prior art. Theweld stud assembly has a head having a weldment area defined on the weldstud head. A coating is provided to at least apportion of the threads ofthe weld stud assembly to inhibit the adhesion of paint to the threadedarea.

In another aspect of the invention, a cage nut assembly has a bodyhaving a threaded bore, a cage enclosing at least a portion of the bodyand providing a limited range of movement to the body within the cage.The cage has a coating on a surface that is formulated to prevent thedeposit of an electrodeposition coating during further processinginvolving the cage nut assembly.

In yet another aspect of the invention, a cage nut assembly has a bodyhaving a threaded bore, a cage enclosing at least a portion of the bodyand providing a limited range of movement to the body within the cage.The cage has a coating on a surface with the surface tension of thecoating being greater than about 25 mNm⁻¹ and less than about 36 mNm−1.

The invention further provides a weldable metallic fastener with aflange configured to be welded to a surface and a threaded portion atleast partially coated with a coating. The coating is applied as anaqueous composition including a binder, micronizedpolytetrafluoroethylene, and micronized polyethylene. The binderincludes phenoxy resin, epoxy resin, or both. In a further embodiment, aweldable threaded fastener configured to be welded to a surface has acoating on a portion of the fastener, the coating including an epoxymaterial and polyethylene wax.

In another embodiment, a weldable metallic fastener having a baseconfigured to be welded to a surface is coated with a coating comprisinga binder component, a polyethylene wax, and polytetrafluoroethylene. Thebinder component may include an epoxy resin, a phenoxy resin, anacrylonitrile-butadiene-styrene [ABS] copolymer, a different styreniccomponent, another thermoplastic material, or combinations of these.

In yet another embodiment, a metallic fastener is coated with a coatingincluding polytetrafluoroethylene and a binder selected from phenoxyresin, epoxy resins, and combinations of these.

In a method of the invention, an electrodeposition coating is preventedfrom being applied to a portion of a fastener that is configured to becoupled to a surface by coating a portion of the fastener with an epoxycoating including polyethylene wax. The fastener is fastened to a body,and the body is electrodeposition coated. The epoxy coating on theportion of the fastener resists wetting of the electrodepositioncoating, so that the electrodeposition coating does not adhere or caneasily be removed from that portion.

In a further method, a portion of a fastener configured to be coupled toa body is coated with a first coating. The first coating adheres to thefastener and prevents adhesion of a second coating. The fastener is thencoupled to a body and the second coating is applied to the body. Thesecond coating does not adhere to the areas of the fastener with thefirst coating.

In another embodiment, two articles are connected with a threadedfastener. A portion of the threaded fastener is coated with a firstcoating comprising a wax, then the threaded fastener is attached to afirst article. A second coating is applied to the first article andfastener, but the second coating does not coat the portion coated withthe first coating. Finally, a second article is connected to the firstarticle with the threaded fastener.

In yet a further method a vehicle, such as an automotive vehicle isassembled by coating at least a portion of a weldable fastener with afirst coating composition. The coating composition includes a componentthat provides the coating with a surface tension of up to about 30mNm⁻¹. The fastener is welded to a vehicle component that is then coatedby electrodeposition coating, in which step the electrodepositioncoating does not substantially adhere onto the portion of the fastenerthat was coated with the first coating. By this we mean that the eitherno electrodeposition coating covers the portion or that any minor amountthat might impinge on the portion can be easily removed, e.g. bybrushing or knocking it off.

In a still further method, torqueing of a second fastener onto a firstfastener is improved, particularly variation in applied torque isreduced compared to when an uncoated fastener is used, by coating aportion of the first fastener that interfaces with the second fastenerwith an epoxy coating that includes a polyethylene wax. In the method,the first fastener is coated with the epoxy coating including the wax,the fastener is fastened to a body, the body is coated byelectrodeposition (which does not coat the coated first fastenerportion), and, finally, the second fastener is coupled onto the firstfastener.

Finally, the invention provides a method for applying anelectrodeposition paint to a metallic fastener that is configured forcoupling to a surface. A coating composition comprising epoxy resin andone or both of micronized polyethylene wax and micronizedpolytetrafluoroethylene is applied to a portion of the fastener andformed into a solid coating layer before the electrodeposition paint isapplied. The electrodeposition paint does not substantially adhere tothe coating layer.

Further areas of applicability of the present invention will becomeapparent from the detailed description provided hereinafter. It shouldbe understood that the detailed description and specific examples, whileindicating the preferred embodiment of the invention, are intended forpurposes of illustration only and are not intended to limit the scope ofthe invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will become more fully understood from thedetailed description and the accompanying drawings, wherein:

FIG. 1 is a perspective view of the cage nut fastener in its unassembledcondition;

FIG. 2 is a perspective view of the cage nut of the present invention inits assembled configuration;

FIG. 3 is a cross-section of the cage nut in FIG. 2 showing therelationship of the coating with respect to the fastener and the cage;

FIG. 4 is a side view of the drawn arc weld stud according to theteachings of the present invention;

FIG. 5 is a bottom view of the drawn arc weld stud according to FIG. 4;

FIG. 6 is a side view of the drawn arc weld stud according to FIG. 4being coupled to a laminate sheet; and

FIG. 7 represents a chart depicting the required torque to meet apredetermined torque load.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The following description of the preferred embodiment(s) is merelyexemplary in nature and is in no way intended to limit the invention,its application, or uses. While the application describes a weldablecage fastener and a weldable stud, the application is equally applicableto any weldable or other fastener having a surface which resists theadherence of paint, and particularly electrodeposited paints known aselectrocoat [e-coat] or ELPO systems.

The weldable threaded fastener 8 is configured to be coupled to asurface and has a coating on a portion of the threaded fastener. Thefastener is configured to be welded to the surface. Optionally, thefastener is a weldable cage and the coating is on the body of thefastener. Optionally, the coating is on the cage and the fastener has aweldable base. For example, the threaded fastener is a welded stud or awelded nut.

The coating has a surface tension low enough so that a selected secondcoating, preferably an electrodeposition coating, will substantially notadhere to it. In a preferred embodiment, the coating has a surfacetension of greater than 25 and less than 36 mNm⁻¹, and preferablygreater than 27 and less than 32 mNm⁻¹, and most preferably about 28mNm⁻¹, as measured using a Rame-Hart contact angle goniometer whencalculated using harmonic mean. In a preferred embodiment, the coatingcomprises a binder, which includes at least one, but may include aplurality of resin components, and a component that provides the desiredlow surface tension to the surface of the coating. In describing theinvention, “resin” may also, where appropriate, include “polymer” aswell as oligomers and certain monomeric materials (e.g., the diglycidylether of bisphenol A) that are suitable for use in a coating binder.

The coating is formulated to prevent the deposit of a selected secondcoating, e.g. an electrodeposition coating, upon further processing.Although the coating includes a low surface tension binder component,e.g. a siloxane polymer for that purpose, a convenient way to soformulate a coating is to include a low surface tension solid that willcome to the surface as the coating layer is formed. Suitable examples ofmaterials that can provide the desired low surface tension include,without limitation, polyalkylene waxes, particularly polyethylene waxes,and poly(ethylene-copropylene); fluorinated polyalkylenes such aspolytetrafluoroethylene and polyhexaluoropropylene; natural waxes suchas montan and carnauba waxes; certain vinyl polymers, such as poly(vinylfluoride), poly(vinylidene fluoride), and polymers of longer chain vinylesters, such as poly(vinyl butyrate) and poly(vinyl octanoate);non-functional poly(oxyalkylene) waxes such aspoly(oxyalkylene)-dimethylethers like poly(oxyethylene)-dimethyletherwaxes;poly(oxyalkylene)-block-poly(oxydimethylsilylene)-block-poly(oxyalkylene)solid copolymers; and combinations of these.

In another preferred embodiment, the coating comprises a mixture ofpolyethylene and polytetrafluoroethylene. Based on the combined weightsof polyethylene and polytetrafluoroethylene, the coating contains about20 to about 80 weight percent polyethylene, preferably about 30 to about70 weight polyethylene, more preferably about 40 to about 60 weightpercent polyethylene, the remainder being polytetrafluoroethylene.

It is believed that it is particularly beneficial to include a wax as atleast a part of the surface tension-reducing component. Waxes providethe desired surface tension reducing properly to the coating, inaddition, are likely to form a wax-rich layer at the surface of thecoating because a wax will substantially melt at a typical bakingtemperature for the coating. In contrast, certain surfacetension-reducing materials, for example poly (tetrafluoroethylene),would generally not be expected to melt and coalesce at typical coatingbake temperatures.

Fluoropolymers used as a surface modifying component of the coatingcompositions of the invention include generally homopolymers andcopolymers wherein the monomer of the homopolymer or at least one of themonomers of the copolymer contains fluorine. In a preferred embodiment,the fluoropolymers of the invention are prepared from perfluorinatedmonomers.

A preferred class of fluoropolymers includes homopolymers and copolymersof tetrafluoroethylene (TFE). The homopolymer of tetrfluoroethylene isknown as polytetrafluoroethylene, and is commonly available as a line ofTeflon® polymers of Dupont. In another embodiment, the fluoropolymers ofthe invention include copolymers of TFE with hexafluoropropylene (HFP).In another embodiment, fluropolymers are prepared by thecopolymerization of TFE and perfluoroalkylvinyl ethers such asperfluoropropylvinyl ether. Other fluoropolymers of the inventioninclude ethylene/tetrafluoroethylene copolymers, and polyvinylidenefluoride.

Fluoropolymers used in the coating layer of the invention may beprepared by known methods of solution or emulsion polymerization. Thefluoropolymers may be used as emulsions, solutions, or as solidparticles. Aqueous polyethylene and/or polytetrafluoroethylenedispersions are commercially available. In one embodiment, bothpolyethylene and polytetrafluoroethylene are included in the coating.The polyethylene is preferably from about 20 to about 80 weight percent,more preferably from about 40 to about 60 weight percent, based on thecombined total weights of the polyethylene and polytetrafluoroethylene.

With reference to FIGS. 1-6, a weldable threaded fasteners 8 which areconfigured to be coupled to a surface are shown. The fastener has acoating layer 35 configured to resist the adhesion of electro-deposedpaint. Generally, the coating 35 has a binder component and a surfacetension reducing component that resists adhesion to the coated surfaceby a selected second coating, particularly by an electrodepositioncoating.

With reference to FIGS. 1-3, a cage nut fastener, shown generally at 8,has a body 16 coupled to a planar base 12. The body 16 and planar base12 define a threaded through bore 14. Planar base 12 has an upper basesurface 18 and lower base surface 20. The cage nut assembly 8 furtherhas a cage 22 which is generally disposed about the planar base 12. Thecage 22 has a cage upper surface 34 and cage lower surface 32.Additionally, the cage 22 defines two pair of flanges 28. The flanges 28define cutouts 26 which generally correspond to the shape of the body16.

As can be best seen in FIG. 2, the flange elements 28 are folded toenclose the planar base 12 of the body 16. The flanges 28 are positionedso as to restrict the movement away from the cage 22 of the body 16.Additionally, the cutouts 26 are positioned so as to restrict the planarmovement of the body 16 within the assembly.

The cage 22 is configured so the body 16 has a limited range ofmovement. As can be seen in FIGS. 2 and 3, the cage allows slightmovement away from the cage upper surface 34 as well as allowing planarmovement generally parallel to the cage upper surface 34. This planarmovement is generally restricted and defined by the space between thecutouts and the body 16.

As best seen in FIG. 3, the cage 22 has a coating layer 35 (as describedbelow) disposed on a surface which directly faces the hexagonal body 16or planar base 12. This coating provides a surface that has a lowwetability, and preferably has a lower wetability than the body 16. Thissignificantly reduces the amount of wetting of any coatings subsequentlysprayed onto the as coated cage 22. The coating preferably has a surfacetension greater than about 25 mNm⁻¹ and less than about 36 mNm⁻¹. Whilethe coating 35 is shown on the cage 22, it is envisioned that thecoating 35 can equally be applied to the body 16 and/or the planar base12. The coating layer 35 can cover the entire shank 112 or can cover aportion of the shank 112. Further, the coating layer 35 can be placedwithin the threads 117 while leaving the tips of the threads 121 exposed(see FIG. 6).

FIG. 4 represents the drawn arc weld stud 110 according to the teachingsof the present invention. The weld stud 110 is formed of three majorcomponents; a shank 112, a head 114, and an annular weldment area 116.By way of non-limiting example, the shank 112 can be a M6 threadedfastener. Equally, the shank can take the form of pine-tree connector orother sized threaded fastener. The shank 112 defines a coating layer 35(as described below) which resists to adherence of e-coat to thefastener.

The head 114 portion is formed using cold heading methodologies. Thehead 114 for a M6 fastener has an exterior diameter of about 13 mm and athickness of about 2 mm. The head further has a flat lower surface 115having a diameter of about 13 mm. The strength of the fastener is afunction of the thickness of the head. As such, as the thickness of thehead is increased, generally the strength of the fastener 110 isincreased. Increasing the strength of the fastener often leads to anundesirable failure of the interface of the fastener and the laminatematerial. Such failures lead to the fastener being pulled out of thelaminate material, leaving a hole in the thin sheet metal.

The annular weldment area 116 has an exterior radius 118 which equalsthe exterior radius of the lower surface 115 of the head 114. While anannular weldment area 116 is shown, it should be understood thatstandard circular weldment areas, are also applicable. For a M6 studshank, the exterior radius of the head 114 is about 13 mm. The interiorradius of the weldment area 116 has a radius of about 11 mm. Theresulting weldment area being about 150 mm². Each head 114 has athickness T. The thickness 119 of the weldment is approximately 20% to35% of the value of T.

To exemplify the application of this invention, FIG. 6 shows a fusionconnection between a stud 110 and a laminate structure 120. The stud 110corresponds in design to that of FIG. 4 before welding, and reference ismade to the description of FIG. 6 to avoid repetition.

In use, the stud 110 of FIG. 6 is placed in contact with the laminatestructure 120 with the flat edge 22 of the annular weldment area 116touching the laminate structure 120. A welding current is then applied.After application of the welding current, the stud 110 is withdrawn toform an arc. While the arc is burning, both the flat edge 122 of thestud 110 and parts of the structure 120 melt. After a prescribed time,the stud 110 is plunged into the molten metal. The welding current isswitched off before or during plunging. Then, the weld cools down. Asshown in FIG. 6, part of the circumferential edge 122 has melted. Partof the molten metal has entered the cavity 124 defined by the annularweldment area. The weld is substantially annular. The stud 110 and thestructure 120 have a common weld area 126 that has set. Of course, theother illustrated embodiments of this invention operate in similarfashion. After the welding of the stud to the structure, the coatinglayer 35, which has been exposed to a significant amount of heat,retains it capacity to resist the adherence of paint, and particularlye-coat paints.

The coating 35 of the invention functions to prevent or inhibit thedeposit of an electrodeposition coating upon further processing.Preferred coatings have a surface tension such that they are poorlywetted by an aqueous electrodeposition bath. In one aspect, it isbelieved that the lower surface energy of the preferred coatings of theinvention act to prevent deposition at least in part by preventing thesurface of the coated part from being wetted by the electrodepositionbath. The coating 35 may be used to prevent adhesion of other selectedsecond coatings that are applied to uncoated areas of the fastenerand/or the articles to which the fastener is attached.

In one embodiment, the binder component of the coating used to preventadhesion of a further coating layer preferably comprises epoxy resin.The epoxy resin is selected to provide desirable coating properties,e.g. good adhesion and good abrasion resistance so that the coatingremains intact during fabrication with the fastener. In theory, manykinds of epoxy binders are suitable and provide such desirable coatingproperties. The epoxy binder may be thermoset, i.e., crosslinked, or, ifof a suitably high molecular weight, may be thermoplastic. Specificexamples of suitable epoxy resins include, without limitation, bisphenolA-type epoxy resins prepared from the reaction of bisphenol A and thediglycidyl ether of bisphenol A, epoxy novolac resins, phenoxy resins,such resins modified to be water-dispersible (for example, by reactionof terminal epoxide group or of hydroxyl groups with a dicarboxylic acidor a cyclic acid anhydride), and combinations of these. When the coatingcomposition is formulated to be thermosettable, a suitable curing agentor crosslinker is included in the binder. Typical crosslinkers for epoxyresins include, without limitation, dianhydrides, polyamines and aminoresins such as amino formaldehyde resins, polyisocyanate crosslinkers,and polyepoxides (for carboxyl-functionalized resins). In the case ofaqueous coating compositions, the crosslinking resin may be mixed with awater-dispersible epoxy resin before dispersion in the aqueous medium.In a preferred embodiment, the crosslinkers are non-yellowing.Non-yellowing coatings may be desirable in some cases where appearanceis at a premium, or where it is desired to further pigment the coatingto provide a desired surface appearance.

In a preferred embodiment, the coating of the invention includes, basedon combined weights of solid binder and surface tension-reducingcomponent, from about 1 to about 50% by weight of the surfacetension-reducing component. In a preferred embodiment, the surfacetension-reducing component is present in an amount of about 5% by weightor greater, preferably about 10% by weight or more, more preferably fromabout 35% by weight or more, again based on combined weights of solidbinder and surface tension-reducing component. The surface tensionreducing component may be from about 1 to about 70%, more preferablyfrom about 35 to about 60 percent by weight of the combined weights ofsolid binder and surface tension-reducing component. Preferably, thesurface tension-reducing component is present at about 70% by weight orless, and more preferably at about 60% by weight or less, and even morepreferably at about 50% or less, again based on the combined weights ofsolid binder and surface tension reducing component.

The total solids by weight of the coating compositions of the inventionis chosen so as to deliver an appropriate amount of coating to thesurface, and to provide a coating composition with suitable viscosity.The solids content may depend upon whether the coating composition isaqueous or solvent borne, as it is generally desirable to minimizeorganic emissions. For example, preferred coatings 35 may be applied ata weight of about 2 to 9 g/sq. ft., preferably about 3 to 5 g/sq. ft.Generally the percent by weight of the solids in a preferred aqueouscoating composition ranges from about 10% to about 65%. In anotherembodiment, referring still to aqueous compositions, the compositionshave 20% or more by weight solids, preferably 30% or more and morepreferably 35% or more by weight solids. Preferably, the maximum weightpercent solids is 65%, more preferably 60%. In other preferredembodiments, the weight percent solids is 50% or less. In a preferredembodiment, the solids are 45% or less by weight percent. In addition tothe solids, the coating compositions of the invention contain from 1 to40% water, preferably from 5-30% water.

The aqueous coating compositions of the invention may also containorganic solvents to promote a stable dispersion of the binder. In apreferred embodiment, the compositions contain 30% or less organicsolvents, preferably 25% or less. As a general rule, the compositionsmay contain a minimum of 1% organic solvents, preferably a minimum of10% by weight organic solvent. Non-limiting examples of volatile organiccosolvents to be used in the coating compositions include propanol,butanol, ethylene and propylene glycol ethers and ether acetates and1-(2-butoxyethoxy) ethanol.

In addition to the solvents, resin, and surface tension modifier, thecompositions used to form the coating of the invention can containfurther components such as pigments, rheology modifiers, and otherconventional additives. For example, inorganic pigments such as titaniumdioxide, iron oxides, and other oxide pigments or organic pigments maybe added to the coating compositions to provide a desired level ofpigmentation in the coatings.

In another embodiment, the coating compositions of the invention cancontain, in addition to the epoxy resin, a second resin or resins thatprovide further advantages. In a preferred embodiment, the coatingcontains a thermoplastic polymer selected from the group consisting ofthermoplastic elastomer polymers, a styrenic component such as styreniccopolymers, ABS and SAN, a vinyl polymer such as a polyvinyl ester or apoly(vinyl chloride), or other polymers.

Elastomeric polymers include generally polymers based on dienefunctional monomers such as, without limitation, butadiene and isoprene.Non-limiting examples of such polymers include acrylonitrile butadieneelastomer (NBR), butyl rubber (IRR), isobutylene-isoprene elastomer,ethylene-propylene-diene terpolymer (EPDM), ethylene/butane elastomer,ethylene/octane elastomer, isobutylene-paramethylstyrene elastomer(IMS), polybutadiene elastomer (BR), polyisobutylene, polyisoprene (IR),and styrene-butadiene rubber (SBR). Such elastomeric polymers may beprovided as solutions, suspensions, or in a preferred embodiment asparticles. The polymers may be prepared by known processes bycopolymerizing neat monomers, or by carrying out the copolymerization byemulsion polymerization or in solution in organic solvents.

In another embodiment, toughened epoxy resins may be produced by thebulk polymerization of the epoxy in the presence of dissolved rubber orelastomeric polymers as described above. Alternatively, the compositionsof the invention may be prepared by blending the epoxy resin and therubber particles.

The coating compositions of the invention are generally heated or bakedfor a short period of time to dry, coalesce, and, if appropriate toeffect cure or crosslinking, of the coating. In a non-limiting example,the coating may be baked to 375° F. peak metal temperature for 2-5minutes. A typical bake cycle is 400-425° F. for 20-30 minutes. Anappropriate bake cycle for a specific coating depends upon the bindercomponent and may be determined by straight-forward testing.

In a preferred embodiment, the coating composition of the invention isprepared from EPC-1760 E-Coat Block product manufactured byEnvironmental Protective Coatings of Ostrander, Ohio. The E-Coat Blockproduct typically contains less than 5% by weight dimethylethylanolamineand less than 12% by weight of volatile organic solvents such as n-butylalcohol, butylcellosolve, and butylcarbatol. The compositions containfrom about 38 to about 43% by weight solids and have a density of fromabout 8.8 to 9.2 pounds per gallon. As provided, the composition has aZahn cup no. 2 viscosity of 35-45 seconds at 77° F.

In another embodiment of the invention, a metallic fastener 8 isdisclosed having a protective surface coating. The coating 35 is formedfrom a coating containing as a binder epoxy resin, preferably comprisingphenoxy resin, optionally combined with a second, thermoplastic polymer.The coating further contains micronized polyethylene wax, micronizedpolytetrafluoroethylene, and pigment material. The second thermoplasticpolymer preferably includes acrylonitrile-butadiene-styrene copolymer,polyvinyl chloride polymer, or both. The micronized polyethylene wax andthe micronized polytetrafluoroethylene in the coating have a weightratio to each other of about 60 to about 40 weight percent micronizedpolyethylene to about 40 to about 60 weight percent micronizedpolytetrafluoroethylene. Preferably, the solid binder and thepolyethylene and polytetrafluoroethylene coating have a weight ratio toeach other of about 40 to about 60 weight percent binder to about 60 toabout 40 weight percent of the polyethylene and polytetrafluoroethylene.

In another embodiment of the present invention, a fastener is coatedwith an aqueous coating composition. The aqueous coating comprises, asbinder, dispersed epoxy resin, preferable comprising phenoxy resin, andoptionally comprising a second thermoplastic resin. The binder may alsoinclude a bisphenol A-type epoxy resin. The aqueous coating compositionfurther comprises micronized polyethylene wax, micronizedpolytetrafluoroethane, and a pigment material.

In another embodiment of the present invention, a method for applyingelectro-deposition paint to a metallic fastener 8 is disclosed. Thefastener 8 is configured for coupling to a surface and has a coating 35on a portion of the fastener with a protective coating composition asdescribed above.

After applying the electro-deposition paint to a metallic fastener 8,the fastener and the protective coating precursor suspension are curedat about 400 degrees F. for about 30 minutes. After the fastener 8 iscoupled to the structure, an electro-deposition paint is applied to thefastener. The portion of the fastener 8 coated with cured protectivecoating precursor defines a surface portion of the fastener where theelectro-deposition paint will not contact metal of the fastener when theelectro-deposition paint is applied.

In a particularly preferred embodiment, the fastener is coated with acomposition including about 12 to about 20 weight percent binderparticles comprising epoxy resin and thermoplastic resin, the epoxyresin phase derived from bisphenol A and epichlorohydrin, thethermoplastic resin phase derived from blendedacrylonitrile-butadiene-styrene copolymer and polyvinyl chloridepolymer; about 5 to 12 weight percent micronized polyethylene wax; about2 to about 8 weight percent micronized polytetrafluoroethane; about 2 toabout 20 weight percent pigment; about 25 to about 65 weight percentwater; about 50 to about 20 weight percent organic cosolvent; and about0.5 to about 2 weight percent of a neutralizing amine. The coating coatsa threaded region of the fastener. The fastener may be fastened, e.g. bywelding, to a body prior to applying the coating composition.

The threaded second fastener attachment portion of the first fastenercoated with the protective coating defines a surface portion of thefirst fastener where the electro-deposition paint is repelled when theelectro-deposition paint is applied.

Referring to FIGS. 1-3, the cage nut has a body defining a threaded boretherethrough. A cage is disposed about at least a portion of the body.The cage provides a limited range of movement of the body within thecage. Further, the cage has a coating on at least one surface which hasa surface tension of greater than 25 and less than 36 mNm⁻¹ andpreferably greater than 27 and less than 32 mNm⁻¹ and most preferablyabout 28-29 mNm⁻¹, as measured using a Rame-Hart contact anglegoniometer when calculated using harmonic mean. The body has a planarbase while the cage defines a pair of flanges which cover at least aportion of the base. The coating is disposed between the flanges and thebase.

The cage has flange members disposed about a least a portion of the bodyand is configured to limit the range of motion of the body. The body isdisposed on the cage upper surface. The cage has at least one surfacecoated with a layer which is configured to function to prevent thedeposit of an electrodeposition coating upon further processing and hasa lower surface and the coating is further disposed on the lowersurface.

In one embodiment, a weldable threaded fastener configured to be weldedto a surface has a coating on a portion in which coating includes atleast an epoxy material and a wax, preferably a polyethylene wax. Thecoating preferably further includes polytetrafluoroethylene at itssurface. The coating may be thermoplastic or cured. The coatingpreferably has a surface tension of from about 27 mNm⁻¹ to about 32mNm⁻¹. The coating may be on a body portion of the fastener. When thefastener has a weldable cage, such as described with reference to thefigures, the coating may be on the cage.

In another embodiment, the present invention provides a method ofpreventing e-coat from being applied to a fastener, a fastener beingconfigured to be coupled to a surface. The method contains the steps of:a) coating a portion of the fastener with an epoxy coating including awax, particularly a polyethylene wax; b) fastening the fastener to abody; and c) e-coating the body, wherein the coating functions to resistwetting of the e-coat. Optionally, fastening the fastener body iswelding the fastener to a body such as welding a cage of a cage nut tothe body.

The wax may include a polyfluoroethylene component. For example, amixture of polyethylene wax and polytetrafluoroethylene may be in theapplied coating composition. The coating formed therefrom will have bothpolyethylene and polytetrafluoroethylene at its surface. If the appliedcoating is baked, the polyethylene may melt and coalesce, and thecoalesced polyethylene may include particulate polyethylene or (if thebake temperature is high enough) may be a mixture of polyethylene andpolytetrafluoroethylene. Preferably, a sufficient amount of polyethyleneand, optionally, polytetrafluoroethylene is included in the coating toprovide a surface tension of less than 36 mNm⁻¹.

The portion of the fastener coated is preferably a threaded portion or abearing region. The coating may contain a pigment as desired, forexample to provide a desired color or gloss.

In a variation of the invention, a portion of a fastener configured tobe coupled to a body is coated with a first coating. The first coatingadheres to the fastener and prevents adhesion of a second coating. Thefastener is then coupled to a body and the second coating, which, forexample and without limitation, may be an electrodeposition coating orother aqueous coating, is applied to the body. The second coating doesnot adhere to the areas of the fastener with the first coating. Thefastener may be coupled with the body in any conventional way, includingwelding, gluing, screwing, riveting, by sliding into a slot, as part ofa threaded nut and bolt or screw combination, and so on. The fastenermay be coupled to the surface of the body in some coupling methods ormay extend through the surface in other methods.

This method may be applied to a method in which two articles areconnected with a threaded fastener. A portion of the threaded fasteneris coated with the first coating, which preferably includes a wax, thenthe threaded fastener is attached to a first article. A second coatingis applied to the first article and fastener, for example by anelectrodeposition coating process, but the second coating does not coatthe portion coated with the first coating. Finally, a second article isconnected to the first article with the threaded fastener. The firstcoating may be thermoset. Among suitable thermoset coatings containing awax are epoxy coatings. One preferred epoxy coating contains a phenoxyresin, which may be thermoplastic or thermoset. The first coating mayhave a particulate surface component, which may be micronizedpolyethylene or another low surface tension material that aids inpreventing the first coating from being coated by the second coating. Itis preferred for the coating to contain both polyethylene andpolytetrafluoroethylene, for example in the relative amounts describedabove. Such coatings as these can be expected to be abrasion resistant.Thus, the coating on the fastener will not be substantially scraped offof the fastener during critical periods of the fabrication process. Thefastener may be weldable, as the fasteners illustrated in the Figures.

A vehicle, such as an automotive vehicle, may be assembled by includingthese method steps. At least a portion of a weldable fastener may becoated with a first coating composition before the fastener is welded toa vehicle component. The coating composition includes a component thatprovides the coating with a surface tension of up to about 30 mNm⁻¹. Thevehicle component is then coated by electrodeposition coating. Becauseof the first coating, the electrodeposition coating does notsubstantially adhere onto the portion of the fastener with the firstcoating. By this we mean that the either no electrodeposition coatingcovers the portion or that any minor amount that might impinge on theportion can be easily removed, e.g. by brushing or knocking it off.

The first coating may be applied as an aqueous coating composition,which would generally contain a minor amount, for example from about 1%to about 40% by weight, of the component that provides the coating witha surface tension of up to about 30 mNm⁻¹. Polymeric materials forproviding the desired surface tension have been described; preferablythe component includes a wax, such as polyethylene wax, and/orpolytetrafluoroethylene.

In another embodiment of the present invention, a method of improvingthe torqueing of a second fastener onto a first fastener. The firstfastener is coupled to a body and is coated with an electro-depositionpaint. The method contains the steps of: a) coating a portion of thefirst fastener with epoxy, preferably comprising a phenoxy resin, and awax, particularly a polyethylene wax; b) fastening the fastener body; c)coating the body with electro-deposition paint, wherein the coatingfunctions to resist the electro-deposition paint; and coupling a secondfastener onto the first fastener. The portion of the first fastener thatis coated is a portion that interfaces with the second fastener duringthe coupling. The interfacing portion may be, for example, a portion ofthe first fastener body or a portion of the first fastener that is athreaded region. The coating makes it possible to couple the fastenersby applying a torque to the second fastener with a variation in torqueless than 36 Nm, preferably less than 30 Nm. This smooth application oftorque is particularly advantageous when the second fastener is coupledusing the automated power tools typical of automotive assemblypractices. The coating typically provides a surface tension of less than36 mNm⁻¹ to the coated portion. The binder portion of the coating mayfurther include a thermoplastic resin, such as ABS or PVC, as mentionedabove. In some instances, it is advantageous for the wax to includepolytetrafluoroethylene. The first fastener may be welded to the body,as when a cage of the first fastener is welded to the body.

The coating compositions preferably contain from about 15% to about 35%,preferably between about 20% and about 30% epoxy resin. In anon-limiting example, the coating composition contains about 26% byweight epoxy resin. In one embodiment, a coating composition is providedaccording to the present invention that forms a wax-rich surface.

FIG. 7 represents a chart depicting the torque in Nm required to couplea nut onto a coated threaded stud. Plots c1 through c4 represent thetorque required to couple a nut onto a threaded stud coated with thecoating according to the teachings of the present invention andsubsequently coated with an electrodeposition paint. Plots e1 through e4represent the torque required to couple a nut onto a threaded studhaving an electrodeposition coating.

As can clearly be seen from the plots, those studs havingelectrodeposition coatings require significantly varying torque loads tocouple the fasteners. As commercial fastener systems measure the torqueload applied to the fastener to determine when a predetermined clampload is reached, variations in the applied torque loads lead tocorresponding undesirable variations in clamp load of a fastened joint.By reducing variation in the torque load, better fastening of joints canbe accomplished.

As can be seen in Plot c1 through c4, those studs having the coatinglayer according to the teachings of the present invention requiresignificantly smoother torque loads to couple with a threaded fastener.Generally, those torque loads are lower than those of the e-coatedfasteners e1-e4.

The variations in torque load are caused by marring and gauling of thee-coat layers between the threads. Variations of the torque are shown toreach greater than 30 Nm and even shown to be greater than 36 Nm whenmeasured at intervals of 0.0075 seconds. As such, the coatings of thepresent invention are configured to provide variations of torque of lessthan 35 Nm, and preferably less than 30 Nm, and preferably less than 10Nm, and most preferably less than 5 Nm when measured at 0.0075 secondintervals.

One advantage of the coating compositions of the invention is that whenthey are applied to the surface to be coated, the coatings can withstandthe harsh conditions and high temperatures associated with welding acoated part to a metal plate or other part of the assembly. For example,to attach a weld stud to a metal plate requires that at least the metalat the end of the stud in contact with the metal plate be heated to atemperature sufficient to melt the metal. Because the stud is generallymade from a material that conducts heat, it is to be expected thatduring the welding process the weld stud as a whole is heated, includingthe layer of the stud directly below the organic coating of theinvention. Nevertheless, the coating compositions of the inventionprovide an adequate coating that survives even the harsh weldingconditions. In a subsequent step, the coatings of the invention adheringto the weld stud or other threaded fasteners of the invention act toprevent undesired deposition of electrocoat compositions in a subsequentelectrodeposition step.

1. A method of preventing electrodeposition coating from being appliedto a portion of a fastener, the fastener being configured to be coupledto a surface, the method comprising the steps of: a) coating a portionof the fastener with an epoxy coating comprising a micronized wax; b)welding the fastener to a body; and c) applying an electrodepositioncoating to the body, wherein the epoxy coating functions to resistwetting of the electrodeposition coating on the coated portion of thefastener.
 2. The method according to claim 1, wherein the epoxy coatingcomprises a polyfluoroethylene component.
 3. The method according toclaim 1, where coating a portion of the fastener is coating a threadedportion of the fastener.
 4. The method according to claim 1, wherein aportion of a bearing region of the fastener is coated in step a).
 5. Themethod according to claim 1, wherein the coating has a surface tensionof less than 36 mNm⁻¹.
 6. The method according to claim 1, wherein thefastener comprises a base configured to be welded to a surface andwherein coating a portion of the fastener is coating a portion of thefastener with a coating comprising polytetrafluoroethylene and apigment.
 7. The method according to claim 1, wherein welding thefastener to a body comprises welding a cage.
 8. A method of coating afastener that is configured to be coupled to a body, the methodcomprising the steps of: a) coating a portion of the fastener with afirst coating comprising epoxy having a micronized wax, wherein thefirst coating adheres to the fastener and further wherein the firstcoating comprises a component that prevents adhesion of a secondcoating; b) welding the fastener to a body; and c) applying the secondcoating to the body and the fastener, wherein the second coating doesnot adhere to the portion of the fastener coated with the first coating.9. The method of coating a fastener according to claim 8, wherein thefirst coating comprises phenoxy resin.
 10. The method of coating afastener according to claim 8, wherein the first coating has a surfacetension of greater that about 25 mNm⁻¹ and less than about 36 mNm⁻¹. 11.The method of coating a fastener according to claim 8, wherein thesecond coating is applied as an aqueous composition.
 12. The method ofcoating a fastener according to claim 8, wherein the second coating isan electrocoat coating.
 13. The method of coating a fastener accordingto claim 8, wherein a coated portion of the fastener comprises athreaded portion of the fastener.
 14. A method of connecting twoarticles with a threaded fastener, the method comprising the steps of:(a) coating at least a portion of a threaded fastener with a firstcoating, wherein said first coating comprises an epoxy coating having amicronized wax; (b) welding the threaded fastener to a first article;(c) applying a second coating onto the first article and the fastener,wherein the second coating does not coat the portion of the threadedfastener coated with the first coating composition; and (d) connecting asecond article to the first article with the threaded fastener.
 15. Themethod according to claim 14, wherein the first coating is a thermosetcoating.
 16. The method according to claim 14, wherein the first coatingcomprises a phenoxy resin.
 17. The method according to claim 14, whereinthe first coating is abrasion resistant.
 18. The method according toclaim 14, wherein the second coating is applied by electro-depositioncoating.